Tasty Blue lets you play as a small goldfish with an insatiable appetite. After being overfed by your owner, you'll escape into the ocean and begin to eat everything that you encounter. The more you eat, the bigger you get. Eat shrimp, turtles, sharks, submarines, houses, airplanes, and more. In addition to the goldfish, you can also play as a dolphin and a shark. The dolphin starts off as an overworked aquarium star, forced to jump through flaming hoops for food. He escapes from captivity by eating his way through the aquarium and taking revenge on his trainer. The shark is the final playable character, an artificial fish created by scientists to save Earth's oceans. It uses self-replicating nano-technology to consume everything in its path and convert their matter into its own. There's no telling how big this shark will get.

Tasty Blue features over 50 levels in the main story mode of the game. There are also 15 more challenging bonus levels to play after the main game has been completed. The levels are spread across three diverse environments in the game: temperate, tropical, and arctic. Tasty Blue can be played by two players on the same computer. This cooperative mode is extremely fun to experience with a friend. Options allow for split screen (horizontal or vertical) or shared screen (this provides more screen space but constrains the movement of players together).